1. Field of the Invention
The present invention relates to an alternating current generator with an improved fan system, and more particularly, to an alternating current generator in which a rotor is provided with fans for producing cooling air.
The instant application claims priority from Japanese Patent Application No. HEI 7-287289, filed Nov. 6, 1995, which is incorporated herein by reference for all purposes.
2. Description of Related Art
U.S. Pat. No. 4,492,885 discloses a conventional alternating current generator in which a rotor is provided with fans to produce cooling air for cooling the alternating current generator itself.
One of the conventional alternating current generators is hereinafter discussed.
FIG. 15 is a sectional view showing the conventional alternating current generator for a car. FIG. 16 is a perspective view showing a rotor of the generator. FIG. 17 is a partial perspective view showing a fan (ventilating portion) 14 which is attached to the rotor.
As shown, the alternator includes a rotor 1, a rotary shaft 11 driven by a driving force transmitted from an internal combustion engine of a car (not shown) by way of a belt (not shown), a pair of Rondel-type field cores 12, and a field winding 13. The alternator further includes a stator 2 having a stator core 21 and a stator winding 22 which faces the rotor 1 at a predetermined distance therefrom. A front bracket 3 and a rear bracket 4, rotatably support the rotor 1 through bearings 31, 41 and securely hold the stator 2 therebetween. Fans 14, 15 are fixed to the Rondel-type field core 12. Blades 14a, 15a are formed by cut-raising the fans 14, 15.
The Rondel-type field cores 12 are formed into a Rondel-shape as shown in FIG. 15 by the steps of forming a low carbon steel or the like into a star shape by forging, etc. and bend-raising a nail portion 12b projecting from a core portion 12a.
With regard to the operation of the conventional alternating current generator of the above-construction, when the rotor 1 is rotated by an external driving force, a magnetic field generated by the field winding 13 surrounds the Rondel-type field cores 12, and the magnetic field passes through the stator winding 22 in conformity with the rotation of the rotor 1, whereby a current is generated on the stator winding 22 and power is generated through a rectifier 5.
Furthermore, when the rotor 1 is rotated, the fans 14 and 15 fixed to the side of the Rondel-type field cores 12 are also rotated, and the blades 14a, 15a revolve, whereby air flow takes place inside the generator. The air flows may be principally divided into: (1) flows (a) and (b) flowing in through an inlet port 3a of the front bracket, passing through the coil end of the stator winding 22, and flowing out through an outlet port 3b of the front bracket, and (2) flows (c) and (d) flowing in through an inlet port 4a of the rear bracket, passing through the rectifier 5 and brush 6, and flowing out through an outlet port 4b of the rear bracket. The inside of the generator is cooled by the air flows.
In the conventional battery charging alternating current generator of the above-mentioned construction and operation, a problem exists in that the space inside the battery charging alternating current generator is limited, making it impossible to enlarge the area of the blades 14a, 15a of the fans 14, 15 and thus improve cooling efficiency, thus resulting in a temperature rise occurring inside the generator. In particular, the surroundings of the stator 2 which generate heat during the power generation, are not sufficiently cooled.
Japanese Laid-Open Patent Publication (unexamined) No.194-65/1984 discloses an alternating current generator in which a fan is bent to be closely and securely fixed to a core. A problem, however, exists in that since the entire fan is bent along the core, a rather complicated shape and assembly process are required. Moreover, the shape of the blades may be disadvantageously deformed.